I think the cross bar to hull connection is similar to the Hobie 18 - so I'll pass on what I did to my 18SX.
Getting the tramp laced tight seems to be important in holding the whole rig rigid. In my case I found the tramp tracks on each hull had worked loose - stainless rivets and aluminum track leading to galvanic corrosion of the aluminum and loose rivets. I only really noticed how loose the tracks had got when I removed the tramp. To correct this we drilled out the old rivets, filled the worn holes in the hull with epoxy/filler and redrilling them, then riveted the tracks back on (the second time we used rivet washers like you should do - the first attempt pulled out after a couple of races ).
Once the tracks were sorted I double grommeted the tramp then laced it with some skinny polyester covered spectra line (I bought a whole roll - it's useful for all sorts of rigging tweaks). This line makes tramp tightening very easy - just don't over do it or you'll rip out the grommits
When I took the cross bars off the hulls to align the rig I noticed the cross bars only make contact with the hulls in a few places (the worn patches). To increase the contact area and hence stiffness I bonded the cross bars to the hulls with 3M 5200 compound on the advice of a wise old local. This gives you enough time to align the rig square as you tighten the hull to cross bar bolts afterwards. A week later I tightened the bolts again and since then the rig seems much stiffer. That combined with some steering tweaks has really improved the feel of the boat.
5200 is great - but don't ever plan on separating them again. I've just researched, and with some advice from the I20 guys, am getting ready to seat the beams on my new Nacra F18. This is a common practice on the Inter-style cross beams.
They recommend using an epoxy / micro-balloon slurry in order to seat the beam. It forms a very hard surface but will not adhere strongly to the beam. The point is to make a socket that is precisely shaped to the beam. To futher encourage release of the beam if you ever need it, you can wax it with a mold release wax before seating it. One other tip given to me was to put a bead of sealant (3M 4200 that is removable) around the perimeter of the joint before joining in order to give a good appearance post cure. Also watch that you don't get epoxy on the beam to hull bolts either or you'll never be able to tighten them. The step by step should be as follows:
- unassemble hull / beam - clean both joining areas with mineral spirits or acetone - mask off the area thoroughly - wax aluminum beam area - apply a dam of 4200 around perimeter of joint and around bolt holes - mix up epoxy slurry to a 'thin peanut butter' consistency - apply epoxy to joint area - rebolt beam in place snugly (not full strength) - clean up perimeter and remove excess epoxy / adhesive using mineral spirits (mineral spirits cleans up 4200 and 5200 very well). Rubbing Alcohol cleans up the epoxy very well. - after epoxy cures, tighten beam bolts to manufacturer specifications.
The Hobie 17 has inboard bolts and outboard castings that fit inside the ends of the cross bars where the meet the hull (at the little hump). Those casting are likely loose. They have two small "fingers" pokeing into the glass structure of the "humps". This is the vertical shear strength of the connection. They are held against the humps by small screws and possibly by sikaflex or 5200.
Dis-assemble the boat and remove the hulls / crossbars. Reseat the castings onto the hulls. You may have to fill the small "finger" holes behind the castings with resin and chopped glass. Re seat the castings with epoxy or 5200 and screws.
Be aware... the position of the castings is critical for a tight boat / ability to re-assemble. Position the castings carefully. Pre-fit with crossbars and check proper positions.
Yeah - the F18 has the same attachment method as all the "Formally known as Inter" boats. They're pre-aligned at the factory and are attached with two bolts through the top of the beam into the hull. There is no adjustment.
The bolt on the inboard lip of the hull is an "active" attachment. Whereas the beam sliding around the casting is a "passive" attachment. I firm that (outboard attachment) up by drilling two hole though the beam and casting on each side. Then rivet the beam to the casting. PLEASE note if the casting is loose this won't do squat. But if it is firm it will work well.
I never realized how much that beam migrated on the casting until i was sailing while sitting on the wing with my foot resting on the rear beam at that point one day.
The rivets helped alot. Also the previously mentioned tricks to "shim" the underside of the beam (wether 5200, microballoons or just an old square of neopreme) help alot also.
When I use to do this with my Tornado the waxing was never successful when I pulled it apart, so I switched to one or two layers of 'Saran wrap". With Saran wrap, pulling apart left the epoxy filler intack, vs waxing which left some epoxy on the beams and some in the pocket.
Latest update, the boat is apart. Ouch, all 4 crossbar castings were broken loose in their sockets. Positioning screws had reamed out holes in the deck and then allowing water into the hulls. The casting fingers had worn enlogated holes into their mounting.
We are drying it out now and expect to begin glassing and building up the structure integrity next week. May use helicoils to better stabalize the casting into the sockets. Will post an update once we get to that point.
Hello to all back online but not at home... i stayed on the beach during the hurricane[ my condo 2nd floor) and have been without power and now house for a few weeks. Although I have some great video of the storm surge hitting my building. Will post later.
As to your beam brackets... I experienced the same problem over time because of all the stress i put on the platform with all my sail area. As mentioned earlier in a previous post the alighnment is very important, I would advise to try and make a template of where the holes are before you start. To be exact will be very difficult,but try to get it close.
you could glass or fill it and while still wet/not kicked slide your beam or a piece of a beam on it while it dries to asure it is a tight fit and will still slide on it when you are done. If u want a piece a beam let me know i'll cut one off for you.
As to my boat, or old boat it. It was an evolution of the 17. The mast is stock + Miracle spreaders(the spin was "noodleing" the mast). Sails all Smyth. Yes those are 8 foot racks i designed (idea stolen from Randy's Nacra Pro 20 / Worrell Rack Monster). I used to race the boat single handed in distance races and had a lot of fun with it.
Bed experience information: I had my crossbar "humps" fixed. The casting was fixed by using epoxy and screw.
ATTENTION: Be carefull with excessive epoxy. Especially in the area between the casting and the hump. If any epoxy is left, the beam will not fit properly back into the hump, and even worse,- the anchor pin is impossible to put back into place
Minor point, but it is easier to put the bolts in first, then thread the anchor pins on. I once set the anchor pins in epoxy, then tired to line up the bolts for assembly, it did not work. The anchor pins pull up in place on the hull as they are screwed in tight. We also tighten the bolts, every day, during a race and after trailing.
We just use the standard folding allen wrench, about 4in, and tighten as tight as possible. Should remove the bolt at least once a season, and check for galling. Also use WD 40 when assembling. Some also suggest backing off the bolt each time, then tightening. This will help eliminate seizing.